Steel Tolerances are Critical
According to a study performed by Charlie Totten of Bethlehem Steel, a substandard crane runways were the number one cause of Overhead Crane downtime. I agree with Charlie and the results of his study and take his study result one step further.
The AISC standards for mill steel is at the heart of runway steel, especially for long span cranes and long support center runways.
Proper runway guidelines can be divided into the following sections;
- · Steel tolerances
- · Runway fabrication
- · Installation tolerances
Runway Steel Tolerances
The installation tolerances can be no better than the tolerances of the steel used in it’s fabrication. Frequently, steel does not meet AISC mill specifications, especially steel from Third World and Eastern European mills. Tolerances must be watched, and materials rejected (or corrected) that do not conform. Adherence to the AISC minimum acceptable tolerance of straightness (paragraph 1-149) is essential.
Here's the startling fact, even if the steel supplied meets AISC/ASTM specifications, it may NOT meet CMAA requirements.